激光增材再制造IN939修复区显微组织与拉伸性能研究

目的 研究采用IN939粉材对镍基高温部件增材修复的可行性,获得增材修复区微观组织与性能分布规律,为燃机部件修复提供支持.方法 探索了IN939合金激光熔覆成形工艺,并进一步开展了IN939增材修复镍基合金梯形槽试验研究,分析了增材修复区显微组织结构与物相组成,研究了激光再制造过程组织变化对修复区显微硬度、拉伸性能的影响.结果 IN939激光修复区形貌良好,组织致密,无明显裂纹、气孔等缺陷.熔覆层主要存在γ奥氏体相和Laves相.IN939修复区由底部至顶部,冷却速率逐渐减小,导致一次枝晶间距逐渐增大,Laves相分布先增多后略有减小.修复区界面处的平均横向残余拉应力为346 MPa.修复区显微硬度由底部至顶部呈现先增大后略有减小的趋势,修复区的平均显微硬度强于基体.修复件的平均屈服强度为548 MPa,极限抗拉强度为959 MPa.激光修复件的拉伸断裂于基体上,显示出IN939合金与基体良好的冶金结合.结论 激光增材修复后,IN939镍基合金修复区的机械性能与结合性能良好,采用IN939粉材进行镍基高温合金的激光增材修复具备可行性.     

铁路货车轮辐板孔裂纹激光再制造

铁路货车轮在辐板孔处产生疲劳裂纹,影响安全运行。文中利用激光熔覆技术,采用镍基合金在车轮辐板辗钢CL60试样表面进行激光再制造试验研究,评价激光再制造试件的组织和性能。结果表明,熔覆层无裂纹、夹杂和气孔等缺陷,与基体形成了良好冶金结合,熔覆层组织是铸态的奥氏体组织,主要由弥散的共晶和亚共晶组成。激光再制造试件力学性能优于车轮基体材料,延伸率提高90%,冲击韧性提高2～3倍,熔覆层的显微硬度提高近50%,疲劳强度提高2.2倍。该工艺用于生产实践,经十万公里试运行考核验证,激光再制造后的车轮满足铁路货运的要求。     

低碳钢电弧熔覆增材层摩擦磨损及抗腐蚀性能

目的 针对低碳钢零件的破损失效采用TIG焊电弧熔覆增材制造工艺，研究低碳钢电弧熔覆修复使其达到再制造零件性能要求的可行性，为实现TIG焊修复应用提供保证。方法 通过TIG焊熔覆在低碳钢坡口处，对熔覆接头的显微组织进行分析，并测试修复后的增材层表面硬度性能。使用Nanovea Tribometer摩擦磨损仪和NanoveaPS50表面轮廓仪，对基体和增材层进行摩擦性能测试，并表征摩擦磨损后的表面形貌，探究磨损机理。采用电化学工作站对基体和增材层的腐蚀性能进行分析。结果 修复后的增材层显微硬度（220.17HV）高于基体且其摩擦性能和腐蚀性能优于基体，随着磨损载荷的增加，增材层的摩擦系数逐渐降低，磨损机制主要为磨粒磨损和粘着磨损。增材层表面组织均匀细小，在NaCl溶液中点蚀坑小且分散，增材层的腐蚀电流密度（1.8349×10-6 A/cm2）小于基体的腐蚀电流密度（6.5251×10-5 A/cm2），增材层表面的抗腐蚀能力明显提高。结论 电弧熔覆低碳钢可满足低碳钢零部件现场电弧快速修复对再制造性能的要求，实现了低碳钢破损零部件的表面修复与强化。     

SCH13钢表面激光熔覆CoNiCrAlY合金

采用2kWCO2激光器在SCH13钢表面激光熔覆CoNiCrAlY合金,选择最佳的工艺参数进行激光熔覆处理,可获得性能优良的熔覆层组织.利用扫描电子显微镜及能谱仪、X射线衍射仪、显微硬度计、磨损试验机对激光熔覆层的微观组织形貌、结构及成分、显微硬度和磨损性能进行了系统分析研究.结果表明,CoNiCrAlY合金激光熔覆层与SCH13钢基体存在良好的冶金结合,熔覆层组织细密,无裂纹,稀释率较低,界面处成分均匀平滑过渡;熔覆层主要由γ-Co,FeCr0.29Ni0.16C0.06,FeNi,CoCx及Cr23C6组成;熔覆层平均显微硬度较基体提高3倍以上,其相对耐磨性较基体提高了3.42倍.     

激光功率对27SiMn钢表面激光熔覆铁基合金组织和性能的影响

为了研究激光功率对激光熔覆修复矿用液压支架立柱的影响,在液压支架立柱母材27Si Mn钢的表面进行了激光熔覆铁基合金试验,分析了不同激光功率下的熔覆层/基体复合材料的显微组织、力学性能和拉伸断口形貌。结果表明,熔覆层的显微组织中多呈现出具有典型定向凝固特征的柱状晶,熔覆层和基体之间实现了良好的冶金结合。不同激光功率下熔覆层的抗拉强度和显微硬度均高于基体,但伸长率相对于基体较低。熔覆层/基体复合材料在拉伸试验的过程中未发生剥离现象,熔覆层的断口形貌表明其为脆性解理断裂,热影响区处的断口形貌呈现出清晰的韧窝,表明其为典型的韧性断裂。     

基于激光熔覆的车床主轴再制造

随着我国可持续发展重大战略的推进,蕴含着高附加值的损伤、退役机床再制造研究越来越受到重视,作为机床的核心部件之一,损伤主轴再制造成为机床再制造的关键。使用Nd∶YAG固体激光熔覆设备及FeCr合金粉料对损伤45钢主轴进行修复再制造研究,使用扫描电镜观察了熔覆层组织结构,通过显微硬度测试、摩擦磨损试验分析了熔覆层硬度及耐磨性,使用磨床对主轴熔覆层进行精密磨削加工。结果表明所得熔覆层无气孔裂纹等缺陷,其硬度达547 HV0.1,相同负载条件下熔覆层耐磨性为基体材料的3.7倍;磨削加工后再制造主轴完全恢复至设计尺寸,经过相同服役时间后再制造主轴磨损量小于新品主轴磨损量,说明了车床主轴激光熔覆再制造的可行性及有效性。     

激光熔覆层宽度对汽轮机转子表面综合跳动特性的影响

为解决大型汽轮机转子轴轴颈磨损的修复问题,基于同轴送粉半导体激光熔覆再制造系统,采用激光熔覆再制造方法,以汽轮机转子轴材料为基体,利用激光熔覆再制造专用粉末作为实验材料,针对不同激光熔覆层宽度对汽轮机转子综合跳动的影响进行实验研究与机理模拟验证。结果表明,综合跳动特性与探头直径和激光熔覆层宽度相关,激光熔覆层宽度决定了汽轮机转子表面磁力线、电涡流密度与磁通量密度分布。当激光再制造层宽度小于8mm时,由于磁力线与表面电涡流密度受基体的干扰,磁通量密度在激光熔覆层的边缘出现突变,实际综合跳动的测量值为基体与激光熔覆层综合作用的结果,造成测量结果偏大。根据数值模拟计算被测金属体表面磁通量密度分布结果,激光熔覆层宽度的临界值为9.82mm。     

42CrMo钢表面激光熔覆颗粒增强Co基涂层的组织与性能

为改进矿用截齿的耐磨性能,使用激光熔覆技术在截齿用42CrMo钢基体表面制备Co基复合涂层,并分析涂层的微观组织、硬度和耐磨性。结果表明,熔覆层形貌良好且与基体呈冶金结合。在激光作用下,WC颗粒发生溶解并与多种元素发生反应,熔覆层主要由γ-(Co, Fe)和碳化物组成。熔覆层组织呈梯度变化,过渡区组织为平面晶、枝状晶和柱状晶,熔覆区组织则为等轴枝晶和均匀分布的富W、Ti的碳化物颗粒。熔覆层平均显微硬度为995 HV,远高于基体(328 HV),同时热影响区的硬度也大幅提高。在相同的磨损条件下,熔覆层摩擦因数较低,体积磨损量仅为基体的13.5%。在摩擦过程中,弥散分布的细小碳化物颗粒逐渐凸起并起到承担载荷和抵抗磨损的作用,使熔覆层具有良好的耐磨性,磨损机制为轻微磨粒磨损。激光熔覆技术制备的颗粒增强Co基涂层,组织致密,性能良好,能显著地提高42CrMo钢的表面硬度和耐磨性。     

激光熔覆层宽度对汽轮机转子表面综合跳动特性的影响（英文）

为解决大型汽轮机转子轴轴颈磨损的修复问题,基于同轴送粉半导体激光熔覆再制造系统,采用激光熔覆再制造方法,以汽轮机转子轴材料为基体,利用激光熔覆再制造专用粉末作为实验材料,针对不同激光熔覆层宽度对汽轮机转子综合跳动的影响进行实验研究与机理模拟验证。结果表明,综合跳动特性与探头直径和激光熔覆层宽度相关,激光熔覆层宽度决定了汽轮机转子表面磁力线、电涡流密度与磁通量密度分布。当激光再制造层宽度小于8 mm时,由于磁力线与表面电涡流密度受基体的干扰,磁通量密度在激光熔覆层的边缘出现突变,实际综合跳动的测量值为基体与激光熔覆层综合作用的结果,造成测量结果偏大。根据数值模拟计算被测金属体表面磁通量密度分布结果,激光熔覆层宽度的临界值为9.82 mm。     

[例37] 激光熔覆在扁头套再制造中的应用

正激光熔覆技术是激光再制造的核心技术之一,它是利用能量极高的大功率激光束,瞬间将被加工件表面微熔,同时使零件表面预置或与激光束同步自动送置的合金粉完全熔化,获得与基体冶金结合的致密覆层的表面修复技术。激光再制造扁头套是利用了激光熔覆技术的以下特点:1激光熔覆层与基体为100%冶金结合,可进行多层重复熔覆恢复损伤尺寸;2基体热影响区极小,产生应力小,激光加工后基本无热     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.